This invention relates to certain novel platinum (O) alkyne complexes and to a novel method of preparing them. By platinum (O) alkyne complexes it is meant herein organometallic platinum complexes with acetylene derivatives as ligands, wherein the platinum atom has a formal oxidation state of zero, as measured by cyclic voltammetry.
Platinum (O) alkyne complexes in general are useful as hydrosilylation catalysts, hydrogenation catalysts, and isomerization catalysts for olefins and alkynes.
Platinum (O) alkyne complexes have a number of advantages over the well known platinum catalyst H.sub.2 PtCl.sub.6.(H.sub.2 O).sub.x, hereinafter referred to as hexachloroplatinic acid. For example platinum (O) alkyne complexes tend to be more compatible with the reactants they are called upon to catalyze. The platinum (O) alkyne complexes are thus more effective, since it is not necessary to provide excess amounts to make up for losses due to precipitation.
Additionally, platinum (O) alkyne complexes are inherently more chemically stable than hexachloroplatinic acid, especially in the presence of moisture.
The synthesis of platinum (O) alkyne complexes is known. For example, F. Gordon A. Stone, Ligand-Free Platinum Compounds, Acc. Chem. Res. 1981, 14, 317-327, describes the synthesis of platinum (O) alkyne complexes using platinum bis(cyclooctadiene) complexes. Unfortunately, the cyclooctadiene complex itself is difficult to make, involving sensitive intermediates which require special handling. These platinum bis(cyclooctadiene) complexes are much more suitable for laboratory preparations than industrial processes.
N. Boag et al., J. C. S. Dalton (1980) pg. 2170 et seq. describe a number of platinum (O) alkyne complexes synthesized via platinum bis(cyclooctadiene) complexes, and platinum tris(ethylene) complexes.
None of the above references describes a method for the synthesis of platinum (O) alkyne complexes that can be practiced without special handling precautions for the intermediates. Moreover, none of the above references disclose the complexes: ##STR1## C.sub.6 H.sub.5 is to be taken throughout this specification and the appended claims as representing the phenyl radical, i.e. ##STR2##